SPS flangesSimulations & Measurements

Update

Fritz Caspers and Jose E. Varela

Outline

• Introduction• Impedance List Update• Damping Resistors in Simulations• Conclusions

Introduction• We continue to search for possible causes of the

suspected 1.4GHz microwave instability in the SPS.

• Last element of the list was simulated and impedance has been included in the table.

• Small study on the possibility of including the damping resistors in simulations has been carried out.

Outline

• Introduction• Impedance List Update• Damping Resistors in Simulations• Conclusions

Total Flange ImpedanceFlange Type Enamel Bellow Num. of

elementsFreq. [GHz] Impedance Q R/Q [Ω] Resistor

BPV-QD Yes Yes 90 1.21 633kΩ 315 2010 No

BPH-QF Yes Yes 39 1.28 1.03MΩ 400 2496 Long

QF-MBA Yes Yes 83 1.41 1.6MΩ 268 5985 Short

MBA-MBA Yes Yes 14 1.41 297kΩ 285 1040 Short

QF-QF No Yes 26 1.41 3.767MΩ 1828 2061 Short

QD-QD Yes No 99 1.57 17kΩ 55 317 No

QF-QF No No 20 1.61 588kΩ 980 600 No

BPH-QF Yes Yes 39 1.62 121kΩ 120 1014 Long

QD-QD No No 75 1.8 651kΩ 881 739 No

QD-QD Yes No 99 1.89 186kΩ 175 1070 No

No damping resistors included in simulations.

The ‘Resistor’ column states whether or not each element should have a resistor.

Outline

• Introduction• Impedance List Update• Damping Resistors in Simulations• Conclusions

Damping Resistor DC Measurement

A 4-wire DC measurement was taken on a long damping resistor as shown in the Figure.

The measured resistance was 160Ω.

A conductivity value of15.7 S/m for the

Nickel-Chrome layer was deduced from the measured

value.

Damping Resistor in SimulationsSimulation

no Resistor

Simulationwith

Resistor

Meas.no

Resistor

Meas.with

Resistor

f [GHz] 1.423 1.414

(-0.68%) 1.417 1.411(-0.42%)

Q0 1910 174 1930 186

The volume of the resistor represents around 1.5% of the total cavity volume.

6% rel. error

Outline

• Introduction• Impedance List Update• Damping Resistors in Simulations• Conclusions

Conclusions• All the elements in the original flange list have

been analysed.

• The impedance, Q and R/Q values have been provided for the bigger resonances.

• A ‘calibration’ of the conductivity value to be used in simulations for the Nickel-Chrome has been carried out.